-Wl,--no-undefined (=-z defs) gives linking errors when used with WITH_ASAN.
According to the documentation:
"When linking shared libraries, the AddressSanitizer run-time is not linked,
so -Wl,-z,defs may cause link errors (don’t use it with AddressSanitizer)."

This patch turns off -Wl,--no-undefined if WITH_ASAN is used.